title: Sorption of perfluorochemicals to granular activated carbon in the presence of ultrasound.
abstract: Perfluorochemicals (PFCs) are emerging pollutants of increasing public health and environmental concern due to their worldwide distribution, environmental persistence, and bioaccumulation potential. Activated carbon adsorption is an effective method to remove PFCs from water. Herein, we report on the sorption of four PFCs: perfluorooctane sulfonate (PFOS), perfluorooctanoate (PFOA), perfluorobutane sulfonate (PFBS), and perfluorobutanoate (PFBA), from deionized water (MQ) and landfill groundwater (GW) by granular activated carbon (GAC) in the absence and presence of 20 kHz ultrasound. In all cases, the adsorption kinetics were found to be well-represented by a pseudosecond-order model, with maximum monolayer sorption capacity and initial sorption rate values following the orders q(e)(PFOS) > q(e)(PFOA) > q(e)(PFBS) > q(e)(PFBA) and v(0)(PFOS) > v(0)(PFBS) > v(0)(PFOA) > v(0)(PFBA), respectively. The equilibrium adsorption was quantified by the BET multilayer absorption isotherm, and the monolayer sorption capacity increased with increasing PFC chain length: q(m)(PFOS) > q(m)(PFOA) > q(m)(PFBS) > q(m)(PFBA). The equilibrium PFC sorption constants, q(e) and q(m), and the sorption kinetic constants, v(0) and k(2), were greater in Milli-Q water than in landfill groundwater with or without pretreatment, indicating competition for sorption sites by natural and cocontaminant groundwater organics. Ultrasonic irradiation significantly increased the PFC-GAC sorption kinetics, 250-900%, and slightly increased the extent of PFC equilibrium adsorption, 5-50%. The ultrasonic PFC-GAC sorption kinetics enhancement increased with increasing PFC chain length, suggesting ultrasound acts to increase the PFC diffusion rate into GAC nanopores.
authors.affiliation: W. M. Keck Laboratory, California Institute of Technology, Pasadena, California 91125, USA.
authors.forename: Deming
authors.initials: D
authors.lastname: Zhao
authors.forename: Jie
authors.initials: J
authors.lastname: Cheng
authors.forename: Chad D
authors.initials: CD
authors.lastname: Vecitis
authors.forename: Michael R
authors.initials: MR
authors.lastname: Hoffmann